1. Field
The invention is in the field of supports for exterior structures on building roofs.
2. State of the Art
It is very common in commercial buildings for there to be various types of pipes which are exposed and run along the top of the roofs of such buildings. These pipes may be connected to air conditioning units mounted on a building roof or to various other service units.
Historically, it was common practice for these pipes to be supported above the roof surface at intervals along their length by placing blocks of wood between the roof surface and the pipes. With temperature changes, the pipes expand and contract and, partly because of the large contact surface area between a block and the pipe, the block moves with the pipe. After a period of time, the movement of the block against the roof with the weight of the pipe thereon causes damage to the roof, which usually results in a leak and requires expensive roof repair. Even where the blocks are nailed down to the roof the nails and the wood usually deteriorate in a relatively short time period so that the blocks break loose. Further, wood blocks are difficult to seal so the roof usually leaks about these nail holes.
Various pipe holders that sit on a roof to support the pipes have now been developed and are in common use. For example, U.S. Pat. Nos. 4,502,653 and 4,513,934 show pipe-supporting devices which have substantially flat bottomed bases with pipe supporting structure rising from the base that substantially equally distributes the weight of the pipe over the bottom of the base and thus over the area of the roof in contact with the base. The pipe supporting structures have a substantially U shaped structure having divergent line contacts for receiving and supporting the pipe above the base. In this manner, the pipe is supported in the U with two contact points. This provides for easy sliding movement of the pipe within the support as the pipe expands or contracts. The support of the '653 patent includes a plastic roller in the bottom of the U recess.
A support system for use in supporting pipe, conduit, and various other items and structures has been in use for long periods of time and utilizes struts with various types of clamps made to mate with the struts. Such strut systems are made and sold by various manufacturers such as Unistrut Corporation of Wayne, Mich. It has not been until recently that such strut systems have been used to support pipes, conduit, and other items and structures above building roofs.
U.S. Pat. No. 6,364,256 shows roof top pipe supports similar to those shown in U.S. Pat. Nos. 4,502,653 and 4,513,934, which have substantially flat bottomed bases with pipe supporting structure rising from the base that substantially equally distributes the weight of the pipe over the bottom of the base and thus over the area of the roof in contact with the base. Those bases, in one embodiment, include two raised portions with studs extending therefrom to which a pipe supporting roller or a length of strut can be height adjustably secured between the studs. The standard strut clamps can then be used to hold electrical conduit or pipe.
U.S. Pat. No. 5,217,191 shows heavy bases, generally reinforced concrete, which sit on a foot pad glued to a roof surface and, in one embodiment, support a strut directly on the flat top surface of the base. These heavy reinforced concrete bases are difficult to ship and transport.
U.S. Pat. No. 5,855,342 shows a plastic foam roof mount base which includes a strut embedded in the foam. The standard strut clamps can then be used to hold electrical conduit or pipe to the strut which is held above the roof surface by the plastic foam material. However, it has been found that the foam base material does not hold up well under the sun and weather exposure on a roof. Furthermore, the foam can retain water and small microbes which attract birds that peck the foam thereby causing damage to the foam.
Room remains for a support which can easily accept and support struts above a roof surface and on which a structure to be supported can be easily assembled on site on a roof.